Lens obturating device



Jan. 12, 1937. J. F. LEVENTHAL LENS OBTURATING DEVICE Filed Oct. 22, 1955 IN VENTOR A TTORNE Y Patented 12, 1937 PATENT OFFICE 2,067,771 LENS oaronarmo nav ca Jacob F. Leventhal, New York, N. Y., asaignor to Leventhal Patents, Inc., New York, N. Y., a corporation of Delaware Application October 22, 1935, Serial No. 46,060

2 Claim.

This invention relates to motion picture apparatus having an optical compensating system for producing stationary images of film-pictures from a film advanced at uniform rate of speed and more especially to the type described in my U. S. Patent No. 1,974,573 in which the motion of each film-picture is compensated by plane-parallel refracting means in two successive stages and separate stationary lens-portions rendered alternately eifective and ineffective by obturating means are provided to co-operate in succession with the refracting means to produce successive co-extensive stationary images of the film-picture.

In this invention a single plane-parallel plate instead of a multiplicity of such plates is used. During the first half rotation of the plate a stationary virtual image of a moving film-picture is produced above the optical axis oi the system and during the second half rotation of the plate a stationary virtual image is produced below the optical axis. Two stationary lens portions separated by a line parallel instead of perpendicular (as shown in said patent) to the film-picture frame-lines are alternately rendered effective by novel obturating means. The obturating means of said patent could obviously not be used with a' single plate compensator.

The present obturator has the following characteristics:

i. It is integral with the compensator.

2. During one rotation it alternately renders effective each of the lens portions.

3. Between the periods of lens-efiectivity it provides periods of complete darkness to hide undesired efiects of the single plate compensator.

4. It reduces the time of opening and closing a lens to a minimum.

To better confine light to the individual lensportions a light source having two separate coils is used and a condenser is so arranged as to produce an image of one coil in one lens portion and an image of the other in the other lens portion.

Other objects, novel features and advantages will be apparent from the following specification and accompanying drawing wherein:

Fig. 1 is a side elevation partly in section showing a preferred embodiment of the invention.

Fig. 2 is an end elevation of Fig. 1.

Figs. 3A to 3L, inclusive, show phases of rotation of the obturator.

Referring now -'to Fig. 1, light from the source I comprising the two coils 2A and 2B is collected by the condenser l and concentrated on the dim 5 at the gate 6. The setting of the condenser 4 with respect to the sources 2A and 2B is such that an image 2A of 2A is formed in the lens portion 1A and an image 23' of the source 23 is formed in the lens portion 13. The plane-parallel plate compensator 8 is mounted in a block i8 on an axle 9 (Fig. 2) and operates in timed relationship with the four-picture film feeding sprocket lilthrough the medium of the one to four spur gears II and I! the shafts of which are journalled in the support i3. Integrally mounted with the compensator 8 are the curved obturator portions i4 and I5 subtending angles of about 70 and 150 respectively and the flat portions I6 and ii. The obturator portions are fastened to the block i8 as better shown in Fig. 2 at it.

In Figs. 3A to 3L, 2!! represents a moving filmpicture and ZIB and ZIA stationary virtual images of 20. The lines a, a, whether solid or dotted represent the boundaries of the light beam from 20 to lens IA and the lines b, b, represent the boundaries of the light beamirom 20 to lens 13.

Action of the device is as follows: When the sprocket wheel l makes one-fourth of a revolution it draws the film past gate 8 for a distance of one film picture. At the same time the compensator 8 makes one revolution, during the first half of which the stationary virtual image NE of 20 is produced and during the second half of which ZIA is produced. The relationship of ZIB to lens 73 is indicated by the dash and double-dot line 23, Fig. 3B, and the relationship of MA to 7A is indicated by the dash and double-dot line 2|, Fig. 31-1. The lenses re-image their respective virtual images in registering alignment at a screen plane not shown but fully described in said patent.

At Fig. 3A light is excluded from both lenses by shield i5. At 38 the compensator has rotated through 45 and light is still excluded from both lenses, partly by shield i5 and partly by shield i4. At 3C. the compensator has rotated an additional 15 and the lines I). b, indicate that theshutter is almost completely open with respect to lens 13 but is completely closed with respect to lens 1A as indicated by lines a, a. At 3D the compensator is normal to theoptical axis 22 and light is excluded from lens 1A partly by shield l5 and partly by it and I7.

During the second half of the cycle (3G to 3L) light is excluded from lens 13 but admitted to 7A in a manner similar to that of the first half of the cycle.

plane-parallel light-retracting compensator and two closely-adjacent objectives having parallel axes, obturating means integral with the compensator comprising a large. and a small arcuate peripheral shield diametrically opposed and symmetrically disposed with respect to the compensator faces and a flat shield extending from the axis of rotation to the center oi arc of the larger arcuate shield.

JACOB F. LEVEN'I'HAL. 

